Synergistic flame-retardant compositions



United States Patent O U.S. Cl. 26045.8 Claims ABSTRACT OF THE DISCLOSURE Synergistic flame-retardant compositions comprising a phosphinic acid and 2,3-dicarboXy-5,S-endomethylene- 5,6,7,8,9,9-hexachloro-1,2,3,4,4a,5,8,8a octahydronaphthalene anhydride and its esters and compositions comprising a thermoplastic resin and said synergistic compositions are disclosed.

BACKGROUND OF THE INVENTION The production ofthermoplastic resin compositions which are flame-retardant is of considerable commercial importance in that such articles as castings, moldings, foamed or laminated articles, etc. are required, or at least desired, to be resistant to fire and flame and to possess the ability to endure heat without deterioration. Typical illustrations of applications of such compositions include castings for live electrical contacts which should not be ignited by flame or sparks, structural members such as pipes, wall coverings, wall paneling, windows, etc. and such items as ash trays, waste baskets, fibers and the like.

The use of certain additives for the purpose of reducing the flammability of various thermoplastic polymers is well known to those skilled in the art. Among the additives currently employed for such a use are various specific types of phosphorus-containing compounds. These phosphorus compounds are generally used either alone or in combination with other materials such as aliphatic or aromatic antimonous compounds. Certain analogous materials such as chlorostyrene copolymers, chlorinated paraflin waxes, alone or with antimony oxide or phosphorus compounds are also known to be effective flameretardants for resinous materials. One drawback of many of these known compounds and combinations of compounds, however, has been the fact that generally large amounts, i.e., upwards of 45%, of the additive must be incorporated into the polymer in order to render it reasonably flame-retardant. Such large quantities of additive of times deleteriously alter the properties of the polymer andmoreover, some additives tend to crystallize or oil out of the polymer after a relatively short time of incorporation therein.

Furthermore, these prior art systems generally are thermally unstable and, as such, are not suitable for incorporation into polymeric materials which require high temperature processing conditions because they tend to discolor or otherwise degrade the resultant processed polymer rendering it unfit for ultimate commercial applications. Additionally, most of the prior art additives are liquid in their natural or most common state and therefore may aflect other physical properties of the polymeric material to which they are added.

3,547,876 Patented Dec. 15, 1970 SUMMARY I have now found that superior flameretarding properties can be imparted to thermoplastic polymer by incorporating in to the polymer a synergistic combination or mixture of (A) a compound having the formula:

wherein R and R taken together constitute an oxygen atom or R and R taken separately are, individually, a hydroxy radical, an alkoxy radical of 1-8 carbon atoms, inclusive, or a haloalkoxy radical of 1-4 carbon atoms, inclusive and (B) a phosphinic acid having the formula:

R3POII wherein R represents an aryl radical of 6-10 carbon atoms, inclusive, an alkyl radical of 1-6 carbon atoms, inclusive, a cyano, hydroxy or carboxy substituted alkyl radical of l-4 carbon atoms, inclusive, or an alpha-hydroxybenzyl radical, and R represents hydrogen or R The novel synergistic combinations provide improved flame-retardance over the additives of the prior art and, additionally, generally provide this superior result at lower concentrations than previously believed to be necessary for most of the known additives. The results shown by the use of the above-mentioned flame-retardant combinations are surprising and unexpected in that the combinations provide a greater degree of flame-retardancy than one would expect from the results shown by the use of the components individually, i.e. they are synergistic.

Additionally, the effectiveness of the combinations is achieved in the absence of any third ingredient, such as antimony compounds or chlorinated hydrocarbons. This synergism, moreover, does not appear to be limited to specific combinations, but is broadly applicable to any combination of a compound represented by Formula I and a compound represented by Formula II.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS As mentioned above, the first critical component of my novel flame-retardant compositions is a compound represented by Formula 1, above. These compounds are well known in the art, as are methods of their production, as represented by U.S. Pat. Nos. 3,152,172 and 3,196,191 which patents are hereby incorporated herein by reference.

As disclosed in said references, the compounds of Formula I are generally prepared by first preparing the anhydride, wherein R and R together are oxygen, by the reaction of hexachlorocyclopentadiene and cis-4-cyclohexene-1,2-dicarboxylic anhydride. The free-dicarboxylic acid and the esters may then be prepared from the anhydride by conventional means, i.e. reaction with an appropriate alcohol or substituted alcohol, e.g. phenol. Alternatively, the acid or esters may be prepared by reaction of the hexachlorocyclopentadiene and the diacid or diesters of said cis-4-cyclohexene-1,Z-dicarboxylic anhydride.

The anhydride represented by Formula I is a crystalline solid material having a melting point of about 275 C. The other compounds are also solids of high melting points. The compounds of Formula I may be used in concentrations ranging from about 1.0% to about 20.0%, by weight, based on the weight of the polymer to which they are added.

The second critical component of my novel flameretardant compositions is a phosphinic acid represented by Formula II, above. These acids may be produced by any known procedure, one of which is disclosed in U.S. Pat. No. 2,953,595 and others of which are taught in Kosolapofl, Organophosphorous Compounds, J. Wiley & Sons, New York, N.Y., page 129 et seq. 1950, which publications are hereby incorporated herein by reference.

The phosphinic acid may be incorporated into the polymeric material in concentrations ranging from about 1.0% to about 20.0%, by weight, based on the weight of the polymer to which it is added.

The term aryl radical, as used herein in regard to the sustituents R and R of Formula II, above, is meant to include not only carbon-hydrogen cyclic compounds but also lower alkyl and halogen ring-substituted phenyl compounds and the scope of the instant invention should be construed so as to include compounds falling within this definition.

The ratio of the compound represented by Formula I to the compound represented by Formula II should range from about 3 to 1 to 1 to 3, respectively, in the polymer.

Any thermoplastic polymeric material may be rendered flame-retardant by the incorporation therewith of the above-identified flame-retardant combinations, Specifically, however, the vinyl type polymers, wherein a monomeric material is polymerized, by known methods, e.g. by use of free-radical generating catalysts, irradiation, anionic and cationic catalysts, etc. are those preferred. Examples of the vinyl type polymers which may be used to form my novel compositions are the homopolymers and copolymers of acrylamides and N-substituted acrylarnides, polyvinyl acetates, butadiene copolymers, e.g. acrylonitrile-butadiene-styrene copolymers, the polymers of acrylonitrile e.g. acrylonitrile-styrene copolymers, polyacrylonitrile etc.

Additionally and even more preferably, one may incorporate the flame-retardant synergistic combinations mentioned above into such polymers as the homopolymers and copolymers of styrene, i.e. polystyrene, a-methyl styrene polymers, styrene-acrylonitrile copolymers, etc. the a-olefin polymers, such as the homopolymers and copolymers, etc. containing, as the major constituent thereof, ethylene, propylene, such as polyethylene, including high density polyethylene, polypropylene and the like and the acrylate and methacrylate homopolymers produced from monomers having the formula:

(III) CII2CC wherein R is hydrogen or a methyl radical and R is an alkyl radical having from 1 to 6 carbon atoms, inclusive. Examples of monomers represented by Formula III include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-amyl acrylate, t-amyl acrylate, hexyl acrylate and their corresponding alkyl methacrylates, etc. and copolymers thereof with one another and with minor amounts, i.e. not more than about 10%, by weight, of comonomers such as acrylonitrile, styrene, etc.

Also such polymers as the polyamides, e.g. adipic acidhexamethylenediamine reaction products; the polycarbonates, i.e. phosgene-Bisphenol A reaction products; the so-called impact polymers, i.e. rubber-polymer blends such as blends of polystyrene with 5-10% of butadienestyrene, the ABS type resins, e.g. blends of butadienestryene and styrene-acrylonitrile; blends of grafted polybutadienes etc. with hard, resinous polymers such as terpolymers of methyl methacrylate, styrene and acrylonitrile etc., and flammable plasticized polymers such as plasticized polyvinylchloride, and the like may be made flame-retardant by the incorporation therein of the synergistic combinations discussed hereinabove.

The novel flame-retardant combinations claimed herein may be added to the various polymers, as such, or as individual components, by any known method. That is to say, the flame-retardant components may be added to the polymer, as such, or in combination by 1) milling the polymer and the components on, for example, a two-roll mill, in a Banbury mixer, etc. by (2) molding the components and the polymer simultaneously, by (3) extruding the polymer and components or by (4) merely blending all the materials together in powder or liquid form and thereafter forming the desired ultimate product. Additionally, the flame-retardant components or combination may be added during the production of the polymer, i.e. during the monomer polymerization, provided, however, that the catalyst, etc. other conditions and other ingredients of the polymerization system are inert thereto.

It is also within the scope of the instant invention to incorporate such ingredients as plasticizers, dyes, pigments, heat and light stabilizers, antioxidants, antistatic agents, photochromic materials and the like into the flame-retarded polymer compositions claimed here- The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by Weight unless otherwise specified.

METHOD OF TESTING Any appropriate flame-retardance test may be used to determine the flame-retardant properties of any specific combination of compounds represented by Formulae I and II, above. One test I have found to be reasonably efficient is a modified version of that test identified as ASTM-D-635-56T. The specifications for this test are: a cylindrical extrudate 6-8 in length, 0.045" in diameter is prepared using a melt index apparatus (ASTMD- 1238-627), marked at the 1" and 5" lengths and then supported with its longitudinal axis horizontal. A Bunsen burner with a 1" blue flame is placed under the free end of the strip and is adjusted so that the flame tip is put in contact with the strip end nearest the 5" marking. At the end of 30 seconds, the flame is removed and the specimen is allowed to burn. If the specimen does not continue to burn after the first ignition, it is immediately recontacted with the burner for another 30 seconds. If, after the two burnings, the strip is not burned to the 5" mark, the specimen is designated as non-burning. If the specimen has burned to the 5" mark but not to the 1" mark it is designated as self-extinguishing.

EXAMPLE 1 To parts of polypropylene are added 7.5 parts of dicyclohexyl phosphinic acid and 7.5 parts of 2,3-dicarboxy-5,8-endomethylene-5,6,7,8,9,9 hexachloro-l,2,3,4, 4a,5,8,8a-octahydronaphthalene anhydride (hereinafter sometimes called DEMON). The resultant mixture is placed in a suitable blender and dry-blended for 4 hours. The blended product is then transferred to a melt-index apparatus which is preheated to 250 C. Following one minute of aging a 2.2 kg. weight is placed on the plunger and an extrudate of 6-8 inches in length is obtained. This specimen is marked and tested according to the aboveenumerated flame-retardance test. The results are set forth in Table I, below.

Various other flame-retardant combinations are then incorporated into various other resins according to Example 1 and comparisons are made between the resultant compositions and control compositions. These results wherein R is an aryl radical of 6-10 carbon atoms, inclusive, an alkyl radical of 1-6 carbon atoms, inclusive, a cyano, hydroxy or carboxy substituted alkyl radical of 14 carbon atoms, inclusive, a cyclohexyl radical or an are also set forth 1n Table I, below. a-hydroxybenzyl radical and R 1s hydrogen or R the TABLE I Phosphinic acid Flamest Ex. R R Percent DEMON derivative Percent Polymer results 1 cyclohexyl cyclohexyl 7.5 DEMON Polypropylene Passed 2.. cyclohexyl cyclohexyl 7. 5 ..do Failed. 3.- DEMON Do. 4 phenyl hydrogen Passed phenyl. hydrogen Failed. phenyl phenyl Passed phenyl phenyl Failed. hydrox'ymethyl hydroxymethyl Passed hydroxymethyl hydroxymethyl Failed. 2-eyanpethy1 2cyanoethyl Passed. 2-cyanoethyl 2-cyanoethyl Failed cyclohxyl eyclohexyl Passed cyclohxyl cyclohexyl Failed.

do.. Do.

cyclohexyl /75 butadiene/styrene Passed.

copolymer. cyelohexyl 5 do Failed. DEMON 5 do Do.

cyclohexyl cyclohexyl 10 DEMON. 10 poly(methy1met Passed.

acrylate). cyclohexyl cyclohexyl 10 "i6 .do Failed 2-carboxy-2-hydroxy 2-carboxy-2-hydroxy 10 10 eth ethyl. 2-carboxy-2-hydroxy 2-carboxy-2-hydroxy 10 ..d0

ethyl. ethyl. a-hydroxy-benzyl a-hydroxy-benzyl 10 DEMON 10 a-hydroxy-benzyl a-hydroxy-benzyl 15 l-hydroxy-pentyl 1-hydrox'y-pentyl 15 DEMON 15 l-hydroxy-pentyl l-hydroxy-pentyl 15 p-ehlo o-phenyl phenyl 10 DEMON 10 p-chloro-phenyl phenyl 10 cyclohexyl cyclohexyl 10 Octyldiester 10 do 10 31 cyclohexyl oyelohexyl 10 DEMON 5 32 cyclohexyl cyclohexyl 10 33 .5 DEMON 5 34 cyclohexyl cyclohexyl 1O Methyldiester. 10

do. 10 o Failed 36"... cyclohexyl cyclohexyl 20 DEMON 20 Commercially available Passed.

1 ABS type resin. 37.-....cyelohexyl cyclohexyl 20 do Failed.

20 do Do. 39 eyclohexyl 5 Polypropylene... Passed 40 o 10 do Failed 41 cyclohexyl cyclohexyl 10 Monocarboxy, methyl 5 es 1'. 42 .do

10 do Failed.

l =adipic acid-hexamethylenediamine reaction product.

wherein R and R together constitute an oxygen atom or R and R individually, constitute a hydroxyl radical, an alkoxy radical of 1-8 carbon atoms, inclusive, or haloal koxy radical of 1-4 carbon atoms, inclusive, and (2) a phosphinic acid having the formula:

II IP-P-OH ratio of (1) to (2) ranging from about 3 to 1 to 1 to 3, respectively.

2. A flame-retardant composition according to claim 1 wherein (2) is dicyclohexyl phosphinic acid.

3. A flame-retardant composition according to claim 1 wherein R and R together form an oxygen atom and (2) is dicyclohexyl phosphinic acid.

4. A flame-retardant composition according to claim 1 wherein R and R together form an oxygen atom.

5. A flame-retardant composition according to claim 1 wherein (2) is diphenyl phosphinic acid.

6. A flame-retardant composition comprising a thermoplastic polymer selected from the group consisting of those produced from unsaturated ethylenically monomers, polyamides and polycarbonates having incorporated therein a flame-retarding amount of the composition of claim 1 the mount of each component of the combination being less than that amount at which the component individually functions similarly to the combination in the same polymer.

7. A flame-retarded composition according to claim 6 wherein said thermoplastic polymer is a polyolefin.

8. A flame-retardant composition according to claim 6 wherein said thermoplastic polymer is polyethylene.

7 8 9. A flame-retarded composition according to claim 6 3,322,716 5/1967 Kleen 260-45.7 wherein said thermoplastic polymer is polypropylene. 3,446,822 5/ 1969 Dunkel 260-3463 10. A flame-retarded composition according to claim 6 wherein said thermoplastic polymer is poly(methyl meth- HOSEA TAYLOR, Pflmary EXamlIlel acrylate), (2) is dicyclohexyl phosphinic acid and R and r v HOKE Assistant Examiner R together form an oxygen atom. 0

US. Cl. X.R.

References Cited UNITED STATES PATENTS 3,152,172 10/1964 Roberts 260-468 0 

